Rethreading machine for restricted bores



NOV. 1, 1938. l, H; IHM ET AL 2,135,339

RETHREADING MACHINE FOR' RESTRICTED BORES I Original Filed March 12, 1935 ai( /40\ s y 4 39 |'47"l 42 4 43 l Fly 3 /VA/V H. /f/M,

CHA/@L55 F, Turni Fly' 2 lNvENToRs ATTORNEY Patented Nov. l, 1938'.

UNITED STATESl PATENT OFFICE RETHREADING MACHINE FOR RESTRICTED BORES of Delaware Original application March 12, 1935, Serial No.

10,622. Patent No. this application May 208,147

6 Claims.

This invention relates to a boring machine and more particularly to one which is adapted to be used for rethreading and similar operations in restricted bores of heavy and relatively immovable equipment, such as pressure still headers which may be in place in a furnace. This application is a division of our co-pending application, Serial No. 10,622, filed March 12, 1935, which issued May 17, 1938, as Patent No. 2,117,327.

Heretofore, it has been the practice, when machining operations are required on the threaded parts of equipment such as pressure still headers, to remove them from their places on the tubes in the furnace, and take them to a shop where the machining is done with conventional equipment.` Inasmuch as these fittings are normally securely supported in the furnace and are fastened as firmly as possible toi the tubes to prevent leakage and blowing oi due to internal pressure, this is a very expensive and inconvenient, as Well as timefconsuming procedure. Certain types of alloy tubes are severely weakened and damaged bythe heating which usually accompanies header removal; and in some cases where the tubes are Welded to the headers, the tubes must be cut and destroyed, orat least shortened, before the headers can be taken olf. This applies particularly to the rethreading operations.

l It is an object of this invention to providey aA portable means for doing accurate eld machine boring, rethreading and the likel in heavy and relatively immovable equipment such as pressure still headers.

5 Another object is to provide a means for accurately aligning and positioning a boring ma. chine tool in a restricted bore to operate on the same.

Another object is to provide a compact and I rugged cross-feed means for a boring tool of this type.

Another object is to provide a simple and accurate portable boring and threading machine and guide means therefor, adapted to rethreadf i restricted bores. l /I These and other objects will be further apparent from the following description and from the appended drawing which forms a part/ of this specification and .illustrates an example of ai preferred embodiment of this invert/tion. In the drawing: v

Figure 1 is a side v vation and part sectional view of a rethreading obl in place in a header.

Figure 2 is a vertical vsectional view on line L n n of Figure 1 and iii/names the tool hold- 2,117,327. 'Divided and l16, 1938, Serial No.

ing, ,feeding and guiding means of this embodiment.

Figure 3 is a bottom View of the tool post used in this example.

Figure 4 is an end view and Figure 5 is a top View of the keyed feed bar used in this example.

Referring tothe drawing, and particularly to Figure 1, the' numerall indicates a header, diagrammatically shown here in section and provided with a threaded sleeve II, the latter having a cylindrical bore I2, terminating in a tapered seat I3, and provided with threads I4 into Whichcorrespondingly threaded closure means of any sort may be secured.. The body I5 of the tool embodying this invention is generally cylindrical in shape and is adapted to be aligned with threads I4 by means of a bushing generally designated I6, this bushing comprising an inner sleeve I1 and an outer sleeve I8,.both provided with comf plementary tapered surfaces so .that they may be secured in bore I2 by means of bolts I9. Alignment of bushing I6 with bore I2 is preferably made by the cooperation of sleeve I8 and a tapered face 20 on the outer end of sleeve II, whichv seats on the tapered face I3 of sleeve II.

The body I5 of thev threading/,tool is preferably reduced in section as aty2'I to provide a smooth running it within bushing I6. In order to,control the helicalv feed of the cutting tool a circular yoke 22 is adapted to be clamped on sleeve -II or some other part of header IIJ by means of centering screws 23 and clamping screws 24. These may be alternately'spaced at 60 intervals around the periphery of yoke 22. Yoke 22 has a ,threaded bore 25 of any `convenient diameter/larger than body I5, the pitch of y the threadbeing identical with that ofthreads I 4 in sleeve I I. Inasmuch as the Acme thread form is usually used in` such bores, it Ymay vconveniently be'usedhere as shown. An externally threaded guide bushing 26 is adapted to enter the threaded bore 25, and, with that bore, fulllls the function of guiding the body I5 inthe desired helical path. Bushing 26 is clamped to a shoulder 2T on the outer end of the tool body I5 by means of a wedge ring 28 secured to the body by key 29 and threaded clamp ringv 30. Guide bushing 26 and clamp ring 30 are provided, respectively, With'lugs 3I and 32 so that they may be turned by suitable spanners from outsidel of yoke 22.

The body I5 projects outwardlyfrom yoke- 22 and is provided with a hexagon face 33 so that it may be turned by a wrench or any similar turning means. The feed screw arrangement and/ also the cross-feed ior the cutting or rethreading tool is essentially similar to that shown in our co-pendlng application, now Patent 2,117,327,`

and will be described in detail below.

The threading tool 24 is secured in a generally cylindrical tool post or holder 'as by set screws 36, 21 and 88. Holder 35 is received in a generally transverse bore 88 in body I5, the angle of the bore preferably correspondingto oneside of the thread profile. Holder 85 is movable longitudinally in bore 39 by means of inclined grooves 40, in which are received complementary inclined teeth 4I on a cylindrical feed bar 42 (Figures 4 and 5). Feed bar 42 is positioned ina longitudinal bore 4I in body I5 and is prevented from rotating therein by a key 44 received in keyway 45. Feed bar 42 has an axial threaded bore 46 in which a correspondingly threaded feed screw 41 is received. Feed screw 41 extends' into bore 43 through a smaller bore 48 and is prevented from moving longitudinally therein by a ilange 49, secured in body I5 by a threaded locknut 50. The outer end of feed screw 41 is squared as at 5I to receive a wrench or other turning means so that itr may be turned as desired to traverse the threading tool 84. A

In operation, the centering wedge members or sleeves I1 and I8 are tlrst inserted in bore I2 and are tightened by bolts I8. Yoke 22 is' centered and clamped on the outside of sleeve I I by screws 2l and 24. The body I5 is inserted in bushing I6 and tool holder is traversed or fed outwardly by feed screw 41 until tool 84 engages the outer thread of sleeve II. The threaded guide bushing 28 is then clamped to body I5 by keyed wedge ring 28 and clamp ring 88. The rethreading of sleeve II may then be accomplished in the conventional manner, body I5 being centered by sleeves I1 and I8 of bushing I8 and guided in a helical path by the threaded guide bushing 26 cooperating with threaded yoke 22. The progress of the machining or rethreading may be observed through sight openings 52 which may be spaced at suitable intervals around yoke 22 as shown in Figure 1.

Ii it is desired tov enlarge the counterbore 53 at the bottom of threads I4 in sleeve -I I, this may be done by securing the threaded guide bushing 428 to yoke 22 as by set screws 54, and loosening the threaded clamp ring- SII. This will permit body I5 to rotate in a given xed plane between s -quired, and means for centering the body and also for guiding it in the path which it is desired the tool will take. While a speciiic construction has been described and illustrated to carry out these operations and functions, it is to be underfst'ood that the invention is not limited to that device andall such modications and changes as come within the scope of the appended claims are embraced thereby.

We claim:

1. A machine tool for cutting or remachining a screw thread 2n a restricted bore in a body such as a pressure still header, comprising a boring bar, means for axially aligning said barwith said bore, a substantially transversely extensible cutter carried by said bar, a threaded guide member, means for securing said inember to said body, and means separate from said cutter engageable, respectively, with said bar and said threaded guide member to be rotated by said bar and to guide said bar and said cutter in a helical path determined by the pitch of the threads on said threaded guide member.

2. A machine tool according to claim 1 in which said last named means comprises a threaded bushing andmeans for securing said bushing to said boring bar so that it will be rotated thereby.

3. A machine tool according to claim 1 in which the axis of said transversely extensible cutter is parallel to one side of the proi'lle of the threads to be cut.

4. A machine tool for threading'a restricted bore in a body, comprising a boring bar, means at one end of said bar for axially aligning said bar with said bore, a threaded guide member adapted to be aligned with said bore and to be secured to said body, complementary threaded means secured to the other end of said bar adapted to engage said guide member and to be rotated by said bar to guide the latter in a predetermined helical path, and a cutter on said bar intermediate said axial guide means and said helical guide means.

5. A machine tool according to claim 4 in which said cutter is transversely extensible, and including means operable independently of said boring bar for traversing said cutter. I

6. Avmachine tool for operating in a restricted bore in a body comprising a boring bar, means at one end of said bar for axially aligning said bar with said bore, a threaded guide member adapted to be alignedwith said bore, means for securing said member to said body, complementary threaded guide means encircling the other end of said bar and adapted selectively to engage both the said guide member and the said bar or only said bar, and a transversely extensible cutter on said bar intermediate said axial guide means and said threaded guide means.

IVAN H. IHM. CHARLES F. TU'I'ILE. 

